#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	int j = 1;
	double i = 2.0, sum = 1.0;
	while (i <= 100)
	{
		j = -j;
		sum = sum + j / i;
		i++;
	}
	printf("%.3lf", sum);
	return 0;
}